Problems of copying gstreamer buffer into numpy array

Hi guys,
For the gstreamer buffer(memory:nvvm) we can convert buffer to numpy array, This occurred a critical problem: copy from GPU buffer to CPU buffer,
I want to know, this problem only is for discrete GPUs or involved also for jetson devices? If it’s for both, In the jetson devices the GPU and CPU memory is shared, why this copying is occurred? I want to know those buffers (GPU buffer and CPU buffer) are independent from shared memory?

There are several posts with similar questions:

This is known in python programming. We would suggest write a custom plugin in C instead of using numpy array.